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Study of time-dependent CP-violating asymmetries and flavor oscillations in neutral B decays at the Υ(4S)

  • Author(s): Aubert, B
  • Boutigny, D
  • Gaillard, JM
  • Hicheur, A
  • Karyotakis, Y
  • Lees, JP
  • Robbe, P
  • Tisserand, V
  • Palano, A
  • Pompili, A
  • Chen, GP
  • Chen, JC
  • Qi, ND
  • Rong, G
  • Wang, P
  • Zhu, YS
  • Eigen, G
  • Stugu, B
  • Abrams, GS
  • Borgland, AW
  • Breon, AB
  • Brown, DN
  • Button-Shafer, J
  • Cahn, RN
  • Clark, AR
  • Gill, MS
  • Gritsan, AV
  • Groysman, Y
  • Jacobsen, RG
  • Kadel, RW
  • Kadyk, J
  • Kerth, LT
  • Kolomensky, YG
  • Kral, JF
  • LeClerc, C
  • Levi, ME
  • Lynch, G
  • Oddone, PJ
  • Pripstein, M
  • Roe, NA
  • Romosan, A
  • Ronan, MT
  • Shelkov, VG
  • Telnov, AV
  • Wenzel, WA
  • Harrison, TJ
  • Hawkes, CM
  • Knowles, DJ
  • O'Neale, SW
  • Penny, RC
  • Watson, AT
  • Watson, NK
  • Deppermann, T
  • Goetzen, K
  • Koch, H
  • Kunze, M
  • Lewandowski, B
  • Peters, K
  • Schmuecker, H
  • Steinke, M
  • Barlow, NR
  • Bhimji, W
  • Chevalier, N
  • Clark, PJ
  • Cottingham, WN
  • Foster, B
  • Mackay, C
  • Wilson, FF
  • Abe, K
  • Hearty, C
  • Mattison, TS
  • McKenna, JA
  • Thiessen, D
  • Jolly, S
  • McKemey, AK
  • Blinov, VE
  • Bukin, AD
  • Bukin, DA
  • Buzykaev, AR
  • Golubev, VB
  • Ivanchenko, VN
  • Korol, AA
  • Kravchenko, EA
  • Onuchin, AP
  • Serednyakov, SI
  • Skovpen, YI
  • Telnov, VI
  • Yushkov, AN
  • Best, D
  • Chao, M
  • Kirkby, D
  • Lankford, AJ
  • Mandelkern, M
  • McMahon, S
  • Stoker, DP
  • Arisaka, K
  • Buchanan, C
  • Chun, S
  • MacFarlane, DB
  • Prell, S
  • et al.
Abstract

We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy e + e - collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb -1 recorded at the Υ(4S) resonance and 3.9 fb -1 off resonance. One of the neutral B mesons, which are produced in pairs at the Υ(4S), is fully reconstructed in the CP decay modes J/ΨK S 0 , Ψ(2S)K S 0 , X c1 K S 0 , J/ΨK* 0 (K* 0 →K s 0 π 0 ) and J/ΨK L 0 , or in flavor-eigenstate modes involving D(*)π/ρ/a 1 and J/ΨK* 0 (K* 0 →K + π - ). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B 0 -B̄ 0 oscillation frequency Δm d are measured with a sample of about 6350 fully-reconstructed B 0 decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds Δm d =0.516±0.016(stat)±0.010(syst) ps -1 . The value of the asymmetry amplitude sin 2Β is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B 0 decays in the CP-eigenstate modes. We find sin 2Β=0.59 ±0.14(stat)±0.05(syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |λ|=0.93±0.09(stat)±0.03(syst), which is consistent with the expectation of |λ|=1 for no direct CP violation.

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